Piston cleaning and coating method and apparatus

ABSTRACT

A method and apparatus for washing and drying a piston and thereafter coating the piston skirt with a dry film lubricant coating and oven-curing said coating. In the washing and drying operation the piston is carried through the apparatus on a conveyor, is spun while wash solution is sprayed on it, is spun while rinse water is sprayed on it, is spun to throw off rinse water, and has air blown against it to remove moisture from its surface. A flash chamber is used in the curing step.

This is a divisional of application Ser. No. 08/797,005, filed Feb. 7,1997 now U.S. Pat. No. 5,993,564.

BACKGROUND OF THE INVENTION

The present invention relates generally to a cleaning and coating methodand apparatus and more particularly to a method and apparatus forcleaning and coating pistons.

DESCRIPTION OF RELATED ART

In an internal combustion engine, a piston reciprocates inside acylinder. In order to reduce friction, it is known to coat that part ofthe piston which contacts the cylinder (the piston sidewall or pistonskirt) with a dry film lubricant such as graphite with resin. There areseveral known methods for applying the dry film lubricant coating ontothe piston skirt, including the electrostatic coating method, thedipping method, the spray coating method (air spray or airless spray),the transfer pad printing method, and the screen printing method (silkscreen printing method); see U.S. Pat. Nos. 5,435,872; 5,266,142; and5,257,603, the contents of which are incorporated herein by reference.

As is known, the piston must be washed and dried in preparation forreceiving the dry film lubricant coating. In a prior art process, thepistons to be coated are mounted on a track, or are placed into abasket, which travels through a long tunnel. Each piston is mounted onthe track such that it may not rotate or spin on its axis but is merelycarried along by the track. In the first part of the tunnel, the pistonis sprayed with wash water. In the next stage of the tunnel, the pistonis sprayed with rinse water. In the prior art process the piston wasthen dried by baking the wet piston for an effective period of time at atemperature such as 250° F. to drive off the water, or by blowing heated(heated by gas heating, steam heating, or electric resistance heating)air against the piston. The piston was then refrigerated or airconditioned (or left to stand) to cool it down to approximately 90° F.so that the piston could be at the proper temperature for receiving thedry film lubricant coating. The piston was then coated with the dry filmlubricant coating and was cured at a single preselected cure temperaturefor a preselected period of time, such as, for Molykote D-10, 302° F.for 60-120 minutes or 356° F.-375° F. for 30 minutes.

There is a need for a piston cleaning and coating method and apparatuswhich has a piston washing and drying unit which takes up less valuablefloor space in the plant and which utilizes less energy and moreefficiently and effectively produces coated pistons.

SUMMARY OF THE INVENTION

The invention includes a method for washing and drying a piston. Themethod includes the steps of: (a) providing a piston on a conveyor, (b)carrying the piston on the conveyor to a washing area, and (c) at thewashing area spraying wash solution on the piston while simultaneouslyrotating the piston. The method also includes a step of rotating thepiston about its longitudinal axis at an effective rotational speed tothrow off rinse water. An apparatus to perform the method is alsoprovided. A method of curing a dry film lubricant coating is alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view in largely schematic form of a piston cleaning andcoating apparatus.

FIG. 2 is a plan view of a unit for washing and drying pistons prior toa piston coating operation.

FIG. 3 is a sectional view taken along line 3—3 of FIG. 2.

FIG. 4 is a sectional view taken along line 4—4 of FIG. 2.

FIG. 5 is a plan view of a piston carrier showing the gears and otherfeatures.

FIG. 6 is a cross-sectional view taken along line 6—6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along line 7—7 of FIG. 5.

FIG. 8 is a perspective view of a piston.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Generally, the same number is used to identify the same element whichappears in different Figures. With reference to FIG. 8, there is shown arepresentative piston 10 having a sidewall or skirt or exterior skirtsurface 12, a top or crown or dome 14, a ring band 16 having grooves forreceiving piston rings (not shown), and having a cavity or bottom cavitysurface or opening (shown generally at 18) on the bottom of the pistonopposite the dome 14. With reference to FIG. 1, there is shown atransfer conveyor 22 for transporting pistons to a piston washing anddrying unit 20 which has a loading end 24 and an unloading end 26. Afterthe pistons exit the washing and drying unit 20, they are loaded onto aconveyor 28 for transport into the coating area or coating room 30,which is maintained at positive air pressure and at a preselectedtemperature and humidity level which is most effective for applicationof the coating being used. In the coating room, a dry film lubricant,such as Molykote D-10 from Dow-Corning, is applied by a screenapplication machine or piston coating machine such as a Series 500 FBD/Kmachine from Europa-Siebdruck-Centrum. Preferably two piston coatingmachines 32, 34 are utilized, being fed independently from theshuttle/conveyor 28. Less preferably other coating methods known in theart may be utilized.

After the pistons are coated with uncured coating, they are placed backdome down on conveyor 28 or, more preferably, a second correspondingconveyor immediately beneath conveyor 28. The pistons are then carriedpast a visual inspection station 36, such as an Allen Bradley CVIM II,which includes four cameras 37, two on each side. The cameras 37 willimage the coated area and determine if a default is present. Defectiveparts will then be shunted aside for reprocessing.

The inspected pistons leave the coating room 30 dome down on conveyor38. From conveyor 38, a number of pistons such as ten pistons are spacedout in a row at loading end 40 for transfer to the belt of the baking orcuring oven 41. The ten pistons are pushed forward in formation onto thetravelling belt of oven 41. The pistons traverse first into ahigh-temperature flash chamber 42. The flash chamber is maintained at apreselected temperature and the pistons are baked or maintained at thattemperature in the flash chamber for a preselected retention time. Thepreselected temperature is the maximum or substantially maximumtemperature which will not materially affect adversely the curing orperformance of the coating. The preselected retention time is themaximum or substantially maximum period of time at the preselectedtemperature such that the alloy or material of the piston will not reachor exceed the annealing or hardening temperature of the material of thepiston. For Molykote D-10 this preselected temperature is about 425° F.and for a typical aluminum piston as known in the art this preselectedretention time at 425° F. is four minutes. The flash chamber quicklydrives off the solvents and eliminates cold flow of the coating. Use ofthe flash chamber has the added benefit of significantly reducing theretention time in the regular or main cure portion of the oven. Thepistons proceed from the flash chamber 42 into the main cure chamber 44where the baking temperature is held at an effective regular curetemperature, such as 375° F., which is substantially below the flashchamber temperature, for a retention time of sixteen minutes, which timeis substantially reduced from what it would otherwise be, due to theflash chamber. Upon exit from the main cure chamber 44, the pistonstraverse through the cool-down chamber 46 for handling. At the unloadingend 48 the coated pistons are or can be automatically loaded into trays50 for transport to an automotive or similar facility where they areinstalled.

The cleaning and coating apparatus is preferably completely programmedand controlled through the use of a control computer, such as an AllenBradley PLC5/40. Remote input/output blocks are used for automation ofthe system. The master control station 52 preferably contains a touchscreen 51 such as an Allen Bradley 1400E and a visual inspection screen53.

With reference to FIGS. 5-7, there is shown a carrier 54 which carriesfour pistons through the washing and drying unit 20. Carrier 54 includesa metal gear 56 (preferably stainless steel) having teeth 57, a plasticgear 58 having teeth 59, a plastic gear 60 having teeth 61, and aplastic gear 62 having teeth 63. Extending beneath each gear there is arotatable pipe or hollow tube 64 (preferably stainless steel), a lockcollar 66, a bushing 68, a pipe 70 (preferably stainless steel) which isfixed to square tube 72, and a bushing 74. As can be seen, the squaretube 72 holds the gear units in position and the other elements permitthe gear to rotate. Above each gear is a rotatable plastic pistonfixture 76 upon which the piston to be cleaned is mounted or seated. Thepiston fixture 76 has a top hole or opening 78. Wash water, rinse water,and drying air come up through pipe 64 through opening 78 to wash,rinse, and dry the interior cavity 18 of the piston. Piston fixture 76slides over pipe 64 and locking flange 80 and is locked in place by alocking pin 84 going through hole 82 in locking flange 80 andcorresponding holes in piston fixture 76. Locking pin 84 has a lockingpin ring 86 for removing and inserting the locking pin. Locking flange80 is preferably welded to pipe 64. To accommodate different sizedpistons, piston fixture 76 may be unlocked and removed and replaced by adifferent sized piston fixture.

With reference to FIGS. 2-4, the washing and drying unit 20 is poweredby electric motors 88, preferably DC motors, which are connected bychain drive and appropriate gears and sprockets to drive gears 90(preferably stainless steel) and drive gears 91 (preferably stainlesssteel). Each of drive gears 90 and drive gears 91 is a drive mechanism.As will be discussed herein, drive gears 91 are in the drying portion ofthe unit. A large number of carriers 54 are attached to chains 92, 95,to form a conveyor or conveyor belt or conveyor belt arrangement. Theconveyor or conveyor belt is driven in the direction shown by arrow 93by known drive means such as partially illustrated in FIG. 3. A piston,preferably aluminum or cast iron, is mounted dome up on each pistonfixture 76, see for example, pistons 94, 94 in FIG. 3. Four pistons aremounted on each carrier, but the number of pistons on the carrier may bemore or less.

Heavy plastic sheeting 96 a-f is provided to contain washing and rinsingspray as described herein, the sheeting having cut outs shown in FIG. 4to permit pistons and carriers to move to the next station. Spraynozzles 100-107 are provided to spray wash and rinse water. Each ofthese nozzles has three or four additional corresponding nozzles, asshown in FIG. 4, where nozzle 102 has corresponding nozzles 102 a-d andnozzle 103 has corresponding nozzles 103 a-c.

As shown in FIG. 3, the unit 20 includes an air plenum 110. The airplenum 110 extends across the whole width of the carrier conveyormaintaining the same cross sectional profile as shown in FIG. 3. (Forclarity the plenum 110 is not shown in FIG. 2). At the bottom of the airplenum 110 are a series of slits 6 a-h extending across the width of thecarrier conveyor to form air knives where pressurized air is blown outas an air knife to assist in the drying process. Pressurized air tubes112 provide pressurized air through nozzles 114 to blow off and dry theinterior of each piston.

The washing and drying unit 20 operates as follows. Pistons are conveyedsingle lane, dome down on transfer conveyor 22 to loading end 24 of unit20. Through the use of rotating wheels or a rotatable plastic paddlecontacting or positioned into the bottom or bottom cavity of eachpiston, each piston which passes through is placed into the sameplacement direction on the conveyor 22. Pistons are metered into apositioning station where pistons are readied for load to the washerunit. A loading arm grips the pistons near the ring groove location. Thearm rotates 180 degrees in an upward arc to place the pistons dome uponto the fixtures 76 of carrier 54. The piston is dome up so water maydrain. Once the carrier 54 is loaded with four pistons, the chains 92,95 move the carrier conveyor or conveyor or conveyor belt forward thewidth of one carrier and stop again so that the next carrier 54 may beloaded. Thus, the carrier conveyor indexes forward one carrier at a timeand stops.

Drive gears 90, 91 are spring-loaded and preferably rotate continuouslyin a clockwise direction (viewed from the top as in FIG. 2), beingdriven by electric motors 88. As the carrier conveyor indexes forwardand stops, the teeth 57 of metal gear 56 approach and engage thespinning teeth of drive gear 90, 91 and after engagement are driven bygear 90, 91. Gear 90, 91, being spring-loaded, is pushed back slightlyby gear 56 during this operation. Gear 56 is driven in acounterclockwise direction (viewed from the top as in FIG. 2). Metalgear 56 then drives plastic gear 58, which drives plastic gear 60, whichdrives plastic gear 62. In this way, each piston fixture 76 and thepiston mounted thereon is rotated or spun. The piston is rotated aboutits longitudinal axis, which is defined by and is coextensive with thelongitudinal axis of pipe 64. Shortly thereafter, when the indexed stopis completed, the carrier 54 starts moving forward to the next stationand gear 56 travels forward out of engagement with gear 90, 91, andspring-loaded gear 90, 91 moves slightly forward towards the conveyor,awaiting engagement with the gear 56 of the next carrier 54. The entirecarrier conveyor thus indexes forward the width of one carrier and stopsand the operation is repeated. As can be seen, the gears on the drag-outor shake off stations 205, 208, 211, 213, 214, can be larger size toincrease the speed of the spin and assist in elimination of carry-overof water into the next station.

Less preferably the gears 56 on the carriers 54 can be driven by otherdrive mechanisms such as an oscillating rack gear driven from anadjacent motor or the gears 56 of all the carriers 54 in the stationscan be chain-driven by a single chain (another drive mechanism) whichstretches the length of the conveyor or a series of shorter chains,which chain-drive can oscillate or rotate in a single direction. Lesspreferably a small motor can be mounted on each carrier to drive thegears. All of the drive mechanisms are at the washing and rinsing areasand are adapted to engage the carrier at the area and rotationally drivethe piston fixtures 76.

In FIGS. 2-3, the carrier conveyor is shown as having 22 positions orstations (201-222). As can be seen, drive gears 90, 91 are located atpositions or stations 201, 204-205, 207-208, 210-214, 216-219, and 222.Thus at each of these stations the pistons are spun or rotated. Atstation 201, drive gear 90 drives gear 56 to rotate and properly orientthe piston fixtures 76, to line them up. This is accomplished by a bolton a lock collar 66 (preferably the lock collar beneath metal gear 56)which rotates along with a fixture 76. A proximity switch detects thebolt and stops rotation, thus leaving the fixtures 76 properly aligned.This also happens at station 222.

The total cycle time from one station to the next station is 9.6 secondsbut is adjustable. If spinning or rotation occurs at a station, spinningtakes place for 7.5 seconds; the remaining 2.1 seconds is travel timebetween stations. At the following stations the speed of rotation of thefixtures 76 and their corresponding pistons, stated in terms ofrevolutions per second (rps), is as follows (recalling that rotation orspinning occurs for 7.5 seconds at each station): Stations 204, 207,210, and 212—0.4 rps. Stations 205, 208, and 211—1.2 rps. Stations 213and 214—3.33 rps (preferably at least 2, more preferably at least 2.5,more preferably at least 3, rps). Stations 216-219—0.2 rps. Stations 201and 222—0.75 rps until proximity switch activates. These speeds andtimes are adjustable and may less preferably be in a range ±10%, lesspreferably in a range ±25%, less preferably in a range ±50%, lesspreferably in a range ±100%. Preferably the rotation of each piston iscontinuous in one direction only; far less preferably the rotation mayoscillate back and forth between clockwise and counterclockwise, this isstressful on the motors and machine parts.

Station 204 is the high-pressure wash or prewash station, where thepistons are sprayed at more than 60 psi, more preferably at 80 psi, with110° F.-190° F., more preferably 110° F.-160° F., more preferably 120°F.-150° F. wash solution, the wash solution comprising alkaline orneutral cleaner containing a wetting agent but with no rust inhibitor orsilicon-based foam inhibitor or other foam inhibitor, a preferredcleaner being Product ES1000HD from Environmentally Sensitive Solutions,Milwaukee, Wis. (This same wash solution is used at station 207). Thisstep removes additional chips from the ring grooves. The hightemperature will help to open the porosity of the piston and allow thehigh pressure to displace the oils present. Filtering of the prewashtank is provided. Makeup for the prewash tank is provided from the washtank. Solution level and temperature are sensed and controlled by thecontrol computer. As can be seen, nozzle 101 and corresponding adjacentnozzles 101 a-c (not shown) spray up through pipe 64 to wash theinterior of the piston while nozzle 100, and its corresponding adjacentnozzles 100 a-d (see FIG. 4) spray and wash the outside of the piston.Note in FIG. 4 that the upper nozzles such as 102, 102 a-d, are locatedbetween and above the pistons so that aqueous solutions can be sprayedboth on the top and the side of the pistons. These nozzles canalternatively be lowered so as to be closer to the pistons, but arepreferably maintained between the pistons rather than directly above thepistons so that the side walls or skirts of the pistons may be moreeffectively cleaned. The upper nozzles may be located at other positionsor orientations to clean the exterior surfaces of the pistons.

At station 205 the pistons are spun to shake off wash solution toeliminate carry-over of wash solution to the next station. Similarspinning to shake off water occurs at stations 208 and 211.

Station 207 is the wash station, where nozzles 102, 103 and theircorresponding nozzles spray wash water at 110° F.-160° F., morepreferably 120° F.-150° F., more preferably about 140° F. and 80 psi.Makeup for the wash tank is provided from the rinse tank. Solution leveland temperature are sensed and controlled by the control computer. Ascan be seen, both stations 204 and 207 are washing areas where washsolution is sprayed on the pistons.

Station 210 is a rinse station where nozzles 104, 105 and theircorresponding nozzles spray rinse water at 90° F.-130° F., morepreferably 100° F.-125° F., more preferably about 120° F. and 60 psi.The rinse water is RO (Reverse Osmosis, 7 pH) water from an RO system.The RO system regeneration and operation is controlled by the controlcomputer. RO water is used to minimize the potential for deposits causedfrom minerals found in most water. Solution level and temperature aresensed and controlled by the control computer. The prewash and washtanks have a pH sensor connected to the control computer to maintainproper pH. The RO rinse system has a conductivity probe to maintaincleanliness of the rinse.

Station 212 is the final rinse station where the pistons are sprayed bynozzles 106, 107 with a mist of de-ionized (DI) rinse water at ambienttemperature and 60 psi. Input into the DI unit comes from the RO unitoutput, which has minimal chlorides present. Feeding the DI unit fromthe RO unit helps prolong the DI unit's life cycles. Overspray from theDI station is caught and used to compensate for evaporative loss in therinse station. The DI water is mildly acidic (6-7 pH), and will tend toetch the piston lightly and assist in adhesion of the dry film lubricantcoating. The DI water will sheet off of the piston easier to minimizepotential water spots. The spray of the DI water will also help tonormalized and lower the temperature of the pistons. Check valves willbe used with the spray nozzles in the final rinse station. Both stations210 and 212 are rinsing areas.

De-ionization units perform better when process flow is maintained.Thus, the DI output, when not being sprayed, is sent to the RO holdingtank to further clean that water. The DI unit is regenerated withsulfuric acid, eliminating the introduction of chlorides which come fromthe use of hydrochloric acid. Total chlorides present in the DI sprayrinse water are less than 0.1 ppm. This low chloride content eliminatesthe need for rust inhibitors (which are not present in the variousaqueous media used in the present invention), which can interfere withproper coating of the piston. Chlorides, left on pistons, will causeoxidation and rust, visible most on cast iron.

Stations 213 and 214 are the high-speed spin stations to throw off themaximum amount of water and moisture from the piston. This spin throwsoff or eliminates water from the oil holes and ring grooves, as well asmost moisture on the surface. The rotational speed can be adjusted asneeded to more effectively throw off rinse water. By spinning the wateroff the pistons, the piston temperature can be lowered duringprocessing.

Stations 216-219 are the drying stations. The drying stations utilize apressurized air blow-off in combination with rotation of the pistons tocomplete the drying of the pistons. When the carriers index forward andstop in each of stations 216-219, air plenum 110, which had been raised,is lowered over the pistons while it simultaneously blows pressurizedair (temperature 80° F.-160° F., more preferably 90° F.-130° F., morepreferably about 110° F.) onto the adjacent pistons through slits 6 a-h.In the preferred embodiment, the elevated temperature of the air is dueonly to compression of the air as it is pressurized in a compressor, andnot due to any independent heating of the air by such means as gasheating, steam heating, electric resistance heating, etc. Slits 6 a-hare essentially air knives. As these air knives are lowered over theslowly rotating pistons, they force the water down and off the piston.During the 7.5 second stop, the air knife makes one pass down and onepass back up. Less preferably it can make two or more passes. As can beseen, the slits are moved with respect to the top of the piston duringthe blowing step. Less preferably the air plenum can be rotated 90°about its vertical axis so that the air knives run parallel to theconveyor direction of travel. Less preferably the air plenum in thisorientation can be fixed rather than raised and lowered. Less preferablyother combinations of slits and/or nozzles (all of which are orifices orconstriction orifices) can be used to blow air onto the pistons at thisdrying station. Pressurized air at the same temperature and pressure isalso blown up through pipes 64 by nozzles 114 to dry the interior ofeach piston. At the completion of station 216, air plenum 110 is raisedand the carriers index forward one station, where the drive gears 91reengage and the air plenum 110 again lowers, to repeat the process. Ascan be seen, each piston is blown and spun in the dryer section at fourstations (stations 216-219), and no baking step (such as with air atover 200° F. or at or over 250° F.) is employed in the drying process.

At station 222, an unloading arm configured the same as the loading armis used to remove the pistons (preferably at about 70-115° F., morepreferably about 85-105° F., more preferably about 96° F.) from thecarrier and place them dome down onto conveyor 28 where they areshuttled into the coating room 30. In the coating room the skirt of eachpiston is coated with a dry film lubricant on a piston coating machineas described above, and the coating is then cured in oven 41.

Optionally, an additional set of nozzles and stations can beincorporated between stations 211 and 212 for a ninety-second phosphatecoating and rinse.

Although the preferred embodiments have been described, it is understoodthat various modifications and replacements of the components andmethods may be resorted to without departing from the scope of theinvention as disclosed and claimed herein.

What is claimed is:
 1. An apparatus for washing and drying a pistoncomprising a conveyor, said conveyor comprising a plurality of carriers,each carrier having at least one rotatable piston fixture capable ofcarrying and adapted to carry a piston, one of said carriers being afirst carrier having a first rotatable piston fixture, said apparatushaving a washing area, said conveyor being capable of carrying on saidfirst rotatable piston fixture a piston to said washing area, saidapparatus having a first drive mechanism at said washing area adapted toengage said first carrier when said first carrier is at said washingarea and rotationally drive said first rotatable piston fixture, saidapparatus having a first nozzle at said washing area capable of sprayingwash solution on a first piston mounted on said first rotatable pistonfixture at said washing area, said first drive mechanism being capableof rotating said first rotatable piston fixture and said first pistonmounted thereon at said washing area while said first nozzle isperforming said spraying operation, said apparatus having a shake-offarea, said conveyor being capable of carrying on said first rotatablepiston fixture a piston from said washing area to said shake-off area,said apparatus having a second drive mechanism at said shake-off areaadapted to engage said first carrier when said first carrier is at saidshake-off area and rotationally drive said first rotatable pistonfixture, said second drive mechanism being capable of rotating saidfirst rotatable piston fixture and a second piston mounted thereon atsaid shake-off area to effectively throw off wash solution or rinsewater from said second piston.
 2. An apparatus according to claim 1,each rotatable piston fixture being adapted to rotate a piston mountedthereon about said piston's longitudinal axis.
 3. An apparatus accordingto claim 2, said apparatus having a rinsing area, said conveyor beingcapable of carrying on said first rotatable piston fixture a piston fromsaid washing area to said rinsing area, said apparatus having a thirddrive mechanism at said rinsing area adapted to engage said firstcarrier when said first carrier is at said rinsing area and rotationallydrive said first rotatable piston fixture, said apparatus having asecond nozzle at said rinsing area capable of spraying rinse water on athird piston mounted on said first rotatable piston fixture at saidrinsing area, said third drive mechanism being capable of rotating saidfirst rotatable piston fixture and said third piston mounted thereon atsaid rinsing area while said second nozzle is performing said sprayingoperation.
 4. An apparatus according to claim 3, wherein said shake-offarea is located between said washing area and said rinsing area.
 5. Anapparatus according to claim 3, wherein said shake-off area is locatedafter said rinsing area.
 6. An apparatus according to claim 3, saidapparatus having a drying area located after said rinsing area, saidconveyor being capable of carrying on said first rotatable pistonfixture a piston from said rinsing area to said drying area, saidapparatus having an orifice in fluid communication with a unit providingpressurized air, said orifice being provided at said drying area andbeing adapted to blow and capable of blowing air against a third pistonmounted on said first rotatable piston fixture at said drying area toremove moisture from the surface of said third piston.
 7. An apparatusaccording to claim 6, said apparatus having a further drive mechanism atsaid drying area adapted to engage said first carrier when said firstcarrier is at said drying area and rotationally drive said firstrotatable piston fixture, said further drive mechanism being capable ofrotating said first rotatable piston fixture and said third, pistonmounted thereon while said orifice is blowing air against the surface ofsaid third piston.
 8. An apparatus according to claim 7, said orificebeing moveable with respect to the top of said third piston while saidorifice is blowing air against the surface of said third piston.
 9. Anapparatus according to claim 1, said first piston having an exteriorskirt surface and a bottom cavity surface, said first nozzle beingadapted to spray and capable of spraying wash solution on said exteriorskirt surface from a first direction, said apparatus having a secondnozzle at said washing area adapted to spray and capable of sprayingwash solution on said bottom cavity surface from a second directiondifferent from said first direction.
 10. An apparatus according to claim9, said second nozzle being provided beneath said first piston so thatwash solution may be sprayed from said second nozzle through a tube andonto said bottom cavity surface.
 11. An apparatus according to claim 1,wherein said rotatable piston fixture has a channel along itslongitudinal axis effective for carrying wash solution to the bottomcavity surface of a piston mounted on said rotatable piston fixture. 12.An apparatus for washing and drying a piston comprising a conveyor, saidconveyor comprising a plurality of carriers, each carrier having atleast one rotatable piston fixture capable of carrying and adapted tocarry a piston, one of said carriers being a first carrier having afirst rotatable piston fixture, said apparatus having a washing area,said conveyor being capable of carrying on said first rotatable pistonfixture a piston to said washing area, said apparatus having a firstdrive mechanism at said washing area adapted to engage said firstcarrier when said first carrier is at said washing area and rotationallydrive said first rotatable piston fixture, said apparatus having a firstnozzle at said washing area capable of spraying wash solution on a firstpiston mounted on said first rotatable piston fixture at said washingarea, said first drive mechanism being capable of rotating said firstrotatable piston fixture and said first piston mounted thereon at saidwashing area while said first nozzle is performing said sprayingoperation, said plurality of carriers has a plurality of rotatablepiston fixtures, each said piston fixture having a gear with teeth, eachsaid gear intermeshing with the teeth of the adjacent gear so that whenone gear is driven, the adjacent gear is driven.